Lettuce

Aster Yellows

Pathogen: Aster yellows phytoplasma

Symptoms of aster yellows on lettuce include blanching and chlorosis of the
young heart leaves. The center leaves fail to develop normally and remain as
short, thickened stubs in the middle of the head. Outer leaves become yellow
and twisted. Pink to tan latex deposits collect on the underside of midribs of
affected leaves. If young plants are infected, outer leaves yellow and the
plants may be severely stunted. If older plants are infected, latex spots in the
interior of the head may be the only symptoms.

The aster yellows phytoplasma (formerly known as mycoplasmalike organisms)
overwinters in the body of adult leafhoppers and in perennial or biennial host
plants, including native plants, ornamentals, and weeds such as Russian thistle(Salsola tragus), sowthistle(Sonchus spp.), prickly lettuce(Lactuca serriola), dandelion(Taraxacum offinale), and many others. The principal vector is the aster
leafhopper, Macrosteles
quadrilineatus, although the phytoplasma
can be transmitted by many other species of leafhoppers. Leafhoppers can remain
inoculative for at least 100 days. In some areas, the occurrence of aster
yellows may follow the pattern of leafhopper migration.

Control includes removal of weed reservoirs near lettuce fields,
control of vectors with insecticides, and planting away from earlier lettuce
plantings that contain diseased plants. However, control measures are not usually
warranted. There are no resistant or immune lettuce varieties.

For noncommercial purposes only, any Web site may link directly to this page. FOR ALL OTHER USES or more information, read Legal Notices. Unfortunately, we cannot provide individual solutions to specific pest problems. See our Home page, or in the U.S., contact your local Cooperative Extension office for assistance.